48 The Vertebrate Organ Systems 

 Rana pipiens is classified as follows : 



The genus, Rana, has several other members including R. cates- 

 beiana, the large bullfrog. The arrangement of its body parts is essen- 

 tially the same as that of R. pipiens. 



NATURAL HISTORY OF RANA PIPIENS 



In early spring, a chorus of frog calls is heard from every pond. 

 Underlying the high-pitched notes of the peepers is the low-pitched croak 

 of the ranas. Through much of the United States, the commonest species 

 of this genus is Rana pipiens. Every pond, marsh, and stream has its 

 population of this animal. It is a comparatively small frog, its body 

 being but some three inches in length ; however, when its long powerful 

 hind legs are extended, it appears much larger. 



Often the leopard frog is difficult to see because its color blends 

 so well with the vegetation of its surroundings. Its back is olive green 

 in color, with darker spots margined with white, while beneath, the 

 animal is white. The legs have the same color pattern as the body. 

 R. pipiens can change its color to a slight degree. When it is placed 

 on a light background, it becomes lighter in color ; on a background of 

 dark material, its over-all color is much darker. This change is quite 

 rapid, and undoubtedly has protective value. 



This species has an extremely wide geographic range. It is found 

 from the Sierra-Cascades eastward to the Atlantic in the United States 

 and from southern Canada through Mexico down to Panama. Despite 

 this very wide range, the individuals found show only very slight varia- 

 tions in either appearance or habit. 



Habits. — Like the habits of all other well-adapted animals, those 

 of R. pipiens are well suited to its environment. When the frog is 

 resting on land, the front portion of the body is raised on the short 

 forelegs. The animal is thus in a squatting position with the heavy 

 muscular hindlegs flexed for immediate escape. The least noise or vi- 

 bration of an approaching footstep causes the animal to leap rapidly 



